New mail not showing in Inbox

We are running Exchange 2000 with Outlook 2000 on the desktops. We have 40 users. New mail from within the domain typically displays in the user Inbox immediately. For two users, however, new mail does not display. It shows up in the Inbox only after the individual sends an email. The time reflects the time that the original email was sent. Is there an Outlook or Exchange setting that resolves this issue?